Current-limiting circuit breakers are currently designed to interrupt a fault condition in the early stages of the let-through current waveform to substantially reduce the intensity of the arc that occurs between the contacts during the rapid separation process. To promote the electrodynamic repulsion that occurs between the fixed line strap that supports the line contact and the movable contact arm that supports the movable contact, the line strap is provided with a "reverse loop" configuration. One example of an efficient current-limiting circuit breaker employing such a reverse loop line strap is found within U.S. Pat. No. 4,679,016 which Patent is incorporated herein for purposes of reference.
In order to rapidly de-ionize and thermally quench the arc, an arc chute configuration is employed having good mechanical strength and further having the ability to generate electronegative gases which both de-ionize as well as thermally cool the arc. One example of an arc chute composition having specific gas evolving properties is described within U.S. Pat. No. 4,748,301 which Patent is also incorporated herein for reference purposes.
To prevent the egress of such ionized gases from the circuit breaker enclosure, a sealant material is generally applied to the outside of the circuit breaker enclosure where the line straps exit to join the line strap connecting lugs. With the advent of robotic assembly of the circuit breaker components, it is essential to eliminate as many production steps as possible in order not to interfere with the efficiency of the components assembly process.
One purpose of the instant invention is to provide means for automatically sealing the circuit breaker enclosure from the arc gases generated during circuit interruption without requiring any sealant material on the exterior of the circuit breaker enclosure.